This invention relates to apparatus for electrodepositing aluminum from aprotic, oxygen-free and water-free organo-aluminum electrolytes in general and more particularly to improved apparatus of this nature.
Aluminum electrodeposited from aprotic, oxygen-free and water-free organo-aluminum electrolytes has been found highly suitable for many engineering purposes because of its ductility, freedom from pores, corrosion resistance and ability to be anodized. Such electrolytes, which are known, for instance, from U.S. Pat. Nos. 3,448,127 and 3,418,216 and British Pat. No. 1,001,482, are prepared and stored under oxygen-free and water-free conditions. Since the access of air causes a considerable reduction of the conductivity and the life of these electrolytes because the electrolyte reacts with the oxygen and the moisture of the air, the electrolyte bath must be protected from contact with air as thoroughly as possible. Attempts to carry out the electrodeposition of aluminum in known electroplating apparatus and to accomplish the exclusion of air by covering the electrolytic bath with protective liquids such as paraffin oil or inert gases such as nitrogen, however, have not led to satisfactory results. Such coverings do not provide a reliable protection of the electrolytic bath, since they are repeatedly torn open when the articles to be electroplated are inserted and removed as well as when the electrolyte and/or the articles move. Such operations thus permit air to come into contact with the electrolyte. In addition, the use of an inert gas for protection is not possible since inert gasses mix very easily with the ambient air, so that a closed inert gas layer would not provide reliable air exclusion either.